21606490 has 32 divisors (see below), whose sum is σ = 41504400. Its totient is φ = 8070144.

The previous prime is 21606469. The next prime is 21606491. The reversal of 21606490 is 9460612.

It can be written as a sum of positive squares in 8 ways, for example, as 2866249 + 18740241 = 1693^2 + 4329^2 .

It is not an unprimeable number, because it can be changed into a prime (21606491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24904 + ... + 25756.

Almost surely, 2^21606490 is an apocalyptic number.

21606490 is a deficient number, since it is larger than the sum of its proper divisors (19897910).

21606490 is a wasteful number, since it uses less digits than its factorization.

21606490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1026.

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21606490 is about 4648.2781758410. The cubic root of 21606490 is about 278.5232197344.

The spelling of 21606490 in words is "twenty-one million, six hundred six thousand, four hundred ninety".